I have M60s too in a stereo only setup, and am very happy with their performance. Sooner or later, they will be part of my future HT as well.
Now, should I have gone for M80s, probably yes, even though have never heard them. They say, their sound is very similar, but M80s play louder, and I would assume "fuller" especially in a large room like mine. One thing I have learnt in this new hobby: more is never too much!